One-quarter of people around the world is at risk for having a stroke after age 25, a new study has found.

There was nearly a five-fold difference between the regions with the lowest risk - sub-Saharan Africa - and those with the highest risk in East Asia and Central and Eastern Europe.

Researchers found that the global risk increased from about 23% in 1990 to about 25% in 2016

The US fell in the middle of the pack with about a 19 percent risk for stroke among both sexes.

But in China, the stroke risk after age 25 jumped to nearly 40 percent - the highest among any country examined.

The team, from the University of Washington in Seattle, says the findings are evidence that doctors need to discuss how to prevent strokes earlier in their patients' lives than previously believed.

A new study found that East Asia - namely China - was the region with the highest risk for stroke after age 25 and sub-Saharan Africa was the lowest

Our findings are startling,' said Dr Gregory Roth, an assistant professor of health metrics sciences at the University of Washington.

'It is imperative that physicians warn their patients about preventing strokes and other vascular diseases at earlier points in patients' lives.'

For the study, published in the New England Journal of Medicine, the team used data from the Global Burden of Disease Study - which measures mortality due to diseases, injuries and risk factors.

The authors focused on first-time strokes that were either ischemic - occurring when a blood vessel leading to the brain becomes blocked - or hemorrhagic, a stroke that occurs when a weakened blood vessels bursts.

Data was studied from 195 countries and territories between 1990 and 2016.

Previous studies used age 45 as the beginning of a stroke risk, but this was the first study to lower the age to 25.